Technology Centre Mongstad (TCM) in Norway is the world's first facility dedicated to the testing and development of carbon capture technology of flue gases from both a gas-fired power plant and a refinery. TCM Managing Director Tore Amundsen spoke to Muriel Cozier about what makes TCM so unique.

Deep geological storage of carbon dioxide (CO₂) could offer an essential solution to mitigate greenhouse gas emissions from the continued use of fossil fuels. Currently, CO₂ capture is both costly and energy intensive; it represents about 60% of the cost of the total carbon capture and storage (CCS) chain which is causing a bottleneck in advancement of CCS in China. This paper proposes capturing CO₂ from coal chemical plants where the CO₂ is high purity and relatively cheap to collect, thus offering an early opportunity for industrial-scale full-chain CCS implementation. The total amount of high concentration CO₂ that will be emitted (or is being emitted) by the coal chemical factories approved by the National Development and Reform Commission described in this paper is 42 million tonnes. If all eight projects could utilize CCS, it would be of great significance for mitigating greenhouse gas emissions in China. Basins which may provide storage sites for captured CO₂ in North China are characterized by large sedimentary thicknesses and several sets of reservoir-caprock strata. Some oil fields are nearing depletion and a sub-set of these are potentially suitable for CO₂ enhanced oil recovery (EOR) and CCS demonstration but all these still require detailed geological characterization. The short distance between the high concentration CO₂ sources and potential storage sites should reduce transport costs and complications. The authors believe these high purity sources coupled with EOR or aquifer storage could offer China an opportunity to lead development in this globally beneficial CCS option. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

Many technologies are now being explored to permit the combustion of fossil fuels while achieving CO₂ capture in a state suitable for compression, transporting, and sequestration. Among the chief contenders are processes in which the fuel is first decarbonized, usually by gasification, followed by the use of a shift reaction to produce pure H₂; post-combustion capture, in which the CO₂ is removed from the flue gases either at high temperatures (e.g. carbonate or Ca looping) or at near-ambient temperatures (e.g. amine scrubbing); chemical looping in which the fuel is converted in the presence of a solid oxide carrier, thus producing a stream of gas consisting primarily of CO₂ and H₂O; and finally, oxyfuel combustion in which the fuel is burned in a stream of pure, or nearly pure, oxygen. The latter technology is already being investigated for application with pulverized fuel or coal, but more recently, the possibility of using oxyfuel combustion with circulating fluidized beds has been receiving increasing attention. There is already a 30 MWth demonstration unit operating in Spain, with plans to build a 300 MWe plant. This perspective describes the current status of oxyfuel research and development. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

Porous media compressed air energy storage (PM-CAES) and geologic carbon sequestration (GCS) can potentially be combined when CO₂ is used as the cushion gas. The large increase in density of CO₂ around its critical pressure at near-critical temperature means that a PM-CAES reservoir operated around the CO₂ critical pressure could potentially store more air (energy) for a given pressure rise in the reservoir. One-dimensional (1D) radial TOUGH2 simulations of PM-CAES with CO₂ as the cushion gas have been carried out to investigate pressurization and gas-gas mixing effects. We find that pervasive pressure gradients in PM-CAES make it desirable to position the air-CO₂ interface close to the well, but cushion gas at such locations is subject to strong and undesirable air-CO₂ mixing and subsequent production of CO₂ up the well. To avoid this negative effect, CO₂ cushion gas should be located at the far outer margins of storage reservoirs where mixing will be very slow. In such a configuration, the super-compressibility of CO₂ will not be exploited, but CO₂ can be stored in the GCS context potentially earning significant value for the PM-CAES project depending on the price of carbon. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

The Peng-Robinson equation of state (PR EoS) for liquid-vapor equilibrium is extended to model the solid-vapor (sublimation) and solid-liquid (melting) phase equilibria for carbon dioxide (CO₂). The sublimation behavior is modeled through the re-formulations of the empirically based analytical expressions for the two temperature dependent parameters, a and b in the PR EoS. The melting phase behavior on the other hand is modeled by the coupling of the original and the extended PR EoS and equalization of solid and liquid phase fugacities. Analytical expressions derived based on the extended PR EoS are used to determine thermodynamic and phase equilibrium derivative properties for solid/vapor CO₂. These include internal energy, enthalpy, heat capacity, thermal expansion, and isothermal compressibility coefficients as well as the adiabatic speed of sound. In most cases good agreement with the available experimental data is obtained covering the pressure and temperature ranges 0.1–100 MPa and 100–300 K. A pressure/temperature phase equilibrium diagram for solid-liquid-vapor CO₂ is constructed to demonstrate the overall performance and the limitations of the two EoS as compared to the experimental data spanning the triple point up to 100 MPa pressure. It is shown that the application of the PR EoS along the CO₂ sublimation line gives rise to significant errors. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

The geological sequestration of carbon dioxide (CO₂) has been proposed to be one of the most effective and advanced technologies for reducing CO₂ emissions. Geochemical trapping is regarded as an alternative process for CO₂ sequestration. Carbonate mineralization takes advantage of permeability reduction to seal formations, decreasing the risk of CO₂ leakage and increasing storage safety. Because precipitation rates tend to be faster and the solubility product shows a lower value at higher temperatures, the interaction of calcite and kaolinite-rich rock with CO₂-water is expected to form a scale in geothermal reservoirs. The Ca²⁺ released from rocks can be removed as carbonate minerals during CO₂ injection into aquifer rocks. However, the effects of the amount, timing, and location of carbonate precipitation on the permeability of reservoirs are not clear. In order to predict the time and space of clogging by carbonate precipitation, column flow experiments were performed under various conditions.

Supersaturated carbonate fluids were obtained from the Ogachi, Matsushiro, and Namikata field sites. These were introduced in flow experiments over a wide range of temperatures (20∼185 °C), pH (6∼11), and concentrations of reactants ([Ca] = 18∼850 mg/l) to vary the growth rate of carbonate minerals. The reduction of injectivity shows that fluid flow velocity controls the distribution and amount of carbonate deposition. The product of CO₂ concentration and S.I., defined as the logarithm of the ion activity product per the solubility product, might be the index for predicting the time required for clogging to be observed. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd